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#include <bits/stdc++.h>

using namespace std;

int main () {
	int n;
	cin>>n;
	int up=0, down=0, prevup, prevdn;
	int num;
	cin>>num;
	prevup=num; prevdn=num;
	for (int i = 1; i < n;i++) {
		cin>>num;
		if(num>=prevup && i%2==0) {
				up++;
				prevup=1000001;
		}
		else if(num<=prevup&&i%2==1) {
			up++;
			prevup=-1000001;
		} else {
			prevup=num;
		}
		
		if(num<=prevdn && i%2==0) {
				down++;
				prevdn=1000001;
		}
		else if (num>=prevdn && i%2==1) {
			down++;
			prevdn=-1000001;
		}
		else {
			prevdn=num;
		}
	}
	cout<<min(up,down)<<endl;
}